Making modify usage report params modal

Link action was opening a base level page. Changed to load modal.
Extra benefit of not reloading the table (which takes a long time)
when the user cancels and does not change any parameters.

Change-Id: I9cc1bd08c5555897481b732e4f8ce8e47cf78f2e
Closes-Bug: #1419150

openstack_dashboard/dashboards/admin/metering/tables.py

@@ -25,7 +25,7 @@ class ModifyUsageReportParameters(tables.LinkAction):
     name = "create"
     verbose_name = _("Modify Usage Report Parameters")
     url = "horizon:admin:metering:create"
-    classes = ("btn-create",)
+    classes = ("ajax-modal",)
     icon = "edit"